/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jdbc.object;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Map;
import javax.sql.DataSource;

import org.springframework.jdbc.core.RowMapper;
import org.springframework.lang.Nullable;

/**
 * Reusable RDBMS query in which concrete subclasses must implement
 * the abstract updateRow(ResultSet, int, context) method to update each
 * row of the JDBC ResultSet and optionally map contents into an object.
 *
 * <p>Subclasses can be constructed providing SQL, parameter types
 * and a DataSource. SQL will often vary between subclasses.
 *
 * @author Thomas Risberg
 * @see org.springframework.jdbc.object.SqlQuery
 */
public abstract class UpdatableSqlQuery<T> extends SqlQuery<T> {

    /**
     * Constructor to allow use as a JavaBean
     */
    public UpdatableSqlQuery() {
        setUpdatableResults(true);
    }

    /**
     * Convenient constructor with DataSource and SQL string.
     *
     * @param ds  DataSource to use to get connections
     * @param sql SQL to run
     */
    public UpdatableSqlQuery(DataSource ds, String sql) {
        super(ds, sql);
        setUpdatableResults(true);
    }


    /**
     * Implementation of the superclass template method. This invokes the subclass's
     * implementation of the {@code updateRow()} method.
     */
    @Override
    protected RowMapper<T> newRowMapper(@Nullable Object[] parameters, @Nullable Map<?, ?> context) {
        return new RowMapperImpl(context);
    }

    /**
     * Subclasses must implement this method to update each row of the
     * ResultSet and optionally create object of the result type.
     *
     * @param rs      ResultSet we're working through
     * @param rowNum  row number (from 0) we're up to
     * @param context passed to the execute() method.
     *                It can be {@code null} if no contextual information is need.  If you
     *                need to pass in data for each row, you can pass in a HashMap with
     *                the primary key of the row being the key for the HashMap.  That way
     *                it is easy to locate the updates for each row
     * @return an object of the result type
     * @throws SQLException if there's an error updateing data.
     *                      Subclasses can simply not catch SQLExceptions, relying on the
     *                      framework to clean up.
     */
    protected abstract T updateRow(ResultSet rs, int rowNum, @Nullable Map<?, ?> context) throws SQLException;


    /**
     * Implementation of RowMapper that calls the enclosing
     * class's {@code updateRow()} method for each row.
     */
    protected class RowMapperImpl implements RowMapper<T> {

        @Nullable
        private final Map<?, ?> context;

        public RowMapperImpl(@Nullable Map<?, ?> context) {
            this.context = context;
        }

        @Override
        public T mapRow(ResultSet rs, int rowNum) throws SQLException {
            T result = updateRow(rs, rowNum, this.context);
            rs.updateRow();
            return result;
        }
    }

}
